U.S. Pat. No. 4,768,347 discloses a refrigerant recovery system that includes a compressor having an input coupled through an evaporator and through a solenoid valve to a refrigeration system from which refrigerant is be withdrawn, and an output coupled through a condenser to a refrigerant storage container or tank. The evaporator and condenser are contained within a closed cylindrical canister for heat exchange and oil separation, the canister having an oil drain in the bottom. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery in the event of impending overfill of the container. The scale in the noted patent comprises a platform pivotally mounted by a hinge pin to a support base. A pair of coil springs are captured in compression between the platform and the base adjacent to the pivot-remote edge thereof, and the the limit switch is mounted on the base adjacent to the coil springs.
Although the system disclosed in the noted patent has enjoyed substantial commercial acceptance and success, improvements remain desirable, particularly in connection with construction of the container scale. To be specific, it has been found that manual assembly of the pivot pin to the platform and base can be difficult and time consuming. Further, the coil springs can exhibit inconsistent spring rates, and can collapse during assembly or use, necessitating repair. Adjustment of the scale weight threshold cannot be implemented as readily as desirable.
A general object of the present invention is to provide a scale assembly that can be readily and economically manufactured, that exhibits consistent operating characteristics both from one scale to another and/over an extended useful life for each individual scale, and that is more reliable than spring-type scales of the prior art as described above.
Another and more specific object of the invention is to provide a scale assembly of the described character that produces an electrical output signal upon scale deflection corresponding to weight of a predetermined amount, and in which the deflection threshold and/or limit may be readily adjusted both in the factory and in the field.
A further object of the invention is to provide a refrigerant recovery system, of the type disclosed in the abovenoted patent, which includes an improved recovery tank scale that satisfies one or more of the foregoing objectives.